Aircraft landing gear unlock actuator

ABSTRACT

This disclosure relates to a landing gear system that includes a landing gear strut rotatable between stowed and deployed positions. A lock-stay is connected to the landing gear strut and is movable between locked and unlocked conditions. An unlock actuator is connected to the lock-stay and includes first and second members movable relative to one another. The first member is movable between first and second positions that correspond to the locked and unlocked conditions. A controller is in communication with the unlock actuator and is configured to command the unlock actuator between the first and second positions in response to an input. The second member is permitted to free-drive relative to the first member between the stowed and deployed positions with the lock-stay in the unlocked condition.

This application is a divisional application of U.S. patent applicationNo. 12/131,996, which was filed on Jun. 3, 2008, now U.S. Pat. No.8,123,161, which issued on Feb. 28, 2012.

BACKGROUND

This disclosure relates to an aircraft landing gear unlock actuator.More particularly, this disclosure relates to an unlock actuator thatwhen mechanically jammed will not prevent the landing gear from fullydeploying.

Aircraft employ landing gear arrangements that must be reliably deployedfrom a stowed position during landing. In one type of arrangement, thelanding gear is rotated about a pivot by an extend/retract actuator. Alock-stay is biased over-center to lock the landing gear in a deployedposition.

To retract the landing gear, an unlock actuator pulls the lock-stay fromover-center, which enables the extend/retract actuator to retract thelanding gear to the stowed position. During the locking and unlockingsequence, it is possible for the unlock actuator to experience amechanical jam. It is important that any mechanical jam does not preventthe landing gear from fully deploying during the next landing geardeploy cycle. What is needed is a jam tolerant unlock actuator thatenables the landing gear to be fully deployed regardless of a mechanicaljam.

SUMMARY

This disclosure relates to a landing gear system that includes a landinggear strut rotatable between stowed and deployed positions. A lock-stayis connected to the landing gear strut and is movable between locked andunlocked conditions. An unlock actuator is connected to the lock-stayand includes first and second members movable relative to one another,in one example. The first member is movable between first and secondpositions that correspond to the locked and unlocked conditions. Acontroller is in communication with the unlock actuator and isconfigured to command the unlock actuator between the first and secondpositions in response to an input. The second member is permitted tofree-drive relative to the first member between the stowed and deployedpositions with the lock-stay in the unlocked condition.

These and other features of the application can be best understood fromthe following specification and drawings, the following of which is abrief description.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the example embodiment can be understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

FIGS. 1A-1D schematically illustrate the landing gear in deployed andlocked, deployed and unlocked, retracting and stowed positions,respectively.

FIG. 2 is a schematic view of a control system for the extend/retractand unlock actuators.

FIG. 3 is a perspective cross-sectional view of the unlock actuator.

FIG. 4 is a flow chart depicting a retract and deploy cycle in the eventof a mechanical jam.

FIGS. 5A-10B schematically illustrate the unlock actuator throughout theretract and deploy cycles with a mechanical jam.

DETAILED DESCRIPTION

A retracting cycle of a landing gear 10 is illustrated in FIGS. 1A-1D.FIG. 1A depicts the landing gear 10 in a fully deployed position andlocked. FIG. 1B depicts the landing gear 10 in a fully deployed positionand unlocked. FIG. 1C depicts the landing gear 10 while it is beingretracted. FIG. 1D depicts the landing gear 10 in a stowed position.

The landing gear 10 includes a strut 14 supporting wheels 16. The strut14 is rotatable about a pivot, which is provided by an airframe 12, inresponse to an extend/retract actuator applying a force to an arm 19. Alinkage 20 connects a lower portion of the strut 14 to the airframe 12,for example. A lock-stay 22 is interconnected between the linkage 20 andthe strut 14 to lock the landing gear 10 in the fully deployed positionuntil the pilot retracts the landing gear.

In FIG. 1A, the landing gear 10 is shown locked in the fully deployedposition. The example lock-stay 22 includes first and second links 21,23 pivotally secured to one another at a joint D, best shown in FIG. 1B.One end of the first link 21 is connected to the strut 14 at pivot B. Aportion of the second link 23 is connected to the linkage 20 at pivot C.A biasing member 26 is arranged between the lock-stay 22 and the linkage20 to bias the lock-stay 22 to the locked position shown in FIG. 1A. Anunlock actuator 24 is interconnected between the linkage 20 andlock-stay 22 to pull the joint D from over-center, as depicted by thearrow in FIG. 1B (from the locked position shown in FIG. 1A), so thatthe extend/retract actuator 18 can move the landing gear 10 to a stowedposition.

For the example unlock actuator 24, once the lock-stay 22 has been movedfrom over-center, the unlock actuator 24 free-drives. That is, thelock-stay 22 is no longer moved under the power of the unlock actuator24, but rather, the extend/retract actuator 18 moves the lock-stay 22and unlock actuator 24 as the landing gear 10 is stowed.

A controller 32 is used to control the operation of the landing gear andsense the location of various components. The controller 32 can behardware and/or software and constructed as single or multiple units.For example, a lock position sensor 28 communicates with the controller32 to detect the lock-stay 22 in a locked position, as shownschematically in FIG. 1A. The stowed position sensor 30 communicateswith the controller 32 and detects the position of a portion of thelanding gear 10 to ensure that the landing gear is fully stowed.

Other sensors can be used to detect faults in the operation of thelanding gear. For example, position sensors 50 are associated with theunlock actuator 24 to determine positions of components within theunlock actuator 24, as shown in FIG. 2. The position sensors 50 are incommunication with the controller 32 and are used to evaluate whether afault has occurred. Input and output devices 31, 33 are also incommunication with the controller 32. The input device 31 includes oneor more pilot initiated controls, for example. The output device 33includes a fault indicator or a position indicator, for example.

Referring to FIGS. 2 and 3, the unlock actuator 24 includes a body thathouses a motor 38. The motor 38 drives a screw 42 through gears 40, forexample. A finger tube 44 is driven axially by the screw 42. A guide 46is housed within the finger tube 44 and supports a rod 48. The fingertube 44 and rod 48 are coaxial with one another in the example. Duringnormal operation, the finger tube 44 and rod 48 remain nested with oneanother. Ends 34 are provided by the body 36 and rod 48. The ends 34 areinterconnected between the linkage 20 and lock-stay 22. As shown in FIG.2, the position sensors 50 detect the axially position of the fingertube 44. The actual position of the finger tube 44 relative to acommanded position can indicate a mechanical jam and trigger a fault.

Referring to FIG. 3, one end of the screw 42 is supported by a bearing52. An end of the finger tube 44 includes a nut 54 that is threadinglyreceived by the screw 42. A sleeve 56 is positioned within the body 36and provides a stop 58 that limits the axial travel of the finger tube44. In the example, the axial distance that the finger tube 44 cantravel from “stop to stop” corresponds to the distance needed to pullthe lock-stay 22 from over-center to the unlocked condition.

An end of the finger tube 44 includes first and second sets of fingers62, 64. In the example, the first set of fingers 62 includes hooks 66that cooperate with a lip 60 provided by one side of the guide 46 (shownin FIG. 5B). The first set of fingers 62 are moved radially inward whenthe first set of fingers 62 engage an annular tapered collar 74. Thefirst set of fingers 62 extend axially beyond the second set of fingers64. Referring to FIG. 5B, the guide 46 includes a key 70 that isreceived by a slot 72 that extends axially along a portion of the fingertube 44. The key and slot 70, 72 cooperate with one another to preventrotation of the guide 46 and rod 48.

The operation of the landing gear 10 is schematically illustrated by theflow chart shown in FIG. 4. As shown in block 78, the landing gear 10 isillustrated in a fully deployed position and locked. The lock-stay 22 isbiased in the locked position (with the joint D over-center) by thebiasing member 26. Referring to FIGS. 5A and 5B, the unlock actuator 24is illustrated in the locked position with a “normally” operating unlockactuator. The finger tube 44 has been axially advanced by the screw 42with the motor 38 and gears 40 to the position shown. The first set offingers 62 has been moved radially inwardly by the tapered collar 74(not shown). With the finger tube 44 in the illustrated axial position,the biasing member 26 is able to move the rod 48 a sufficient axialamount to enable the biasing member 26 to move the lock-stay 22 to thelocked position. In the position shown in FIGS. 5A and 5B, the hooks 66engage the lip 60 in preparation for pulling the rod 48 to move thelock-stay 22 to an unlocked condition.

The pilot, for example, provides an input through input device 31 toraise the landing gear, as indicated in block 80. In response to thepilot's command to raise the landing gear 10, the unlock actuator 24axially moves the finger tube 44 with the screw 42 to retract the rod 48and move the lock-stay 22 as shown at blocks 82 and 84. The hooks 66 andlip 60 are interlocked with one another such that the finger tube 44pulls the rod 48 and remains in engagement with the guide 46 even afterthe first set of fingers 62 have moved out of engagement with thetapered collar 74.

A mechanical jam is illustrated in FIGS. 6-10B. The mechanical jamdepicted (block 86) is one in which the screw 42 is unable to retractthe finger tube 44 to its axially retracted position, such as if thescrew 42 and nut 54 have become frozen to one another, as shown in FIG.6. As illustrated at block 88, a fault is triggered for example, byposition sensors 50 (FIG. 2) indicating that the unlock actuator 24 ismalfunctioning and in need of replacement.

Referring to block 90 and FIG. 7, the extend/retract actuator 18 actsupon the landing gear 10 to rotate it to the stowed position. The rod 48is moved axially inward and is permitted to free-drive relative to thefinger tube 44 in response to movement by the extend/retract actuator18. In doing so, the hooks and lip 66, 60 disengage from one anotherpermitting the first set of fingers 62 to move radially outwardlyrelative to the guide 46. The landing gear 10 is fully stowed asindicated at block 92 and the guide 46 and rod 48 are positioned asindicated in FIG. 8.

When the pilot initiates a command to deploy the landing gear 10, asindicated at block 94, the landing gear 10 will fully deploy despite thejammed unlock actuator. Referring to block 96 in FIG. 9, theextend/retract actuator 18 rotates the landing gear 10 to the deployedposition. The rod 48 moves axially outwardly relative to the finger tube44. Even with the finger tube 44 stuck in an undesired position, the rod48 is permitted to free-ride and fully extend in response to movement ofthe extend/retract actuator 18 to permit the lock-stay 22 to lock. Asshown in FIGS. 10A and 10B, the rod 48 decouples from the finger tube44. In one example, the guide 46 is permitted to move past the hooks 66into space 76 since the hooks 66 are arranged radially outward of thelip 60. The biasing member 26 biases the lock-stay 22 to the lockedposition as shown at block 98. If the pilot commands the landing gear toa stowed position, as indicated at block 100, the unlock actuator 24will not permit retraction of the rod 48 and the landing gear 10 willremain locked in the fully deployed position, as indicated at block 102.Faces 77 of protrusions 68 will engage ends 75 of the second set offingers 64 (FIG. 10B) thereby preventing the guide 46 from againentering the finger tube 44. A fault will again be sent, as indicated atblock 104.

In this manner, the landing gear 10 is permitted to cycle from a fullydeployed position to a stowed position with a jammed unlock actuator.The landing gear is also permitted to cycle from the stowed position toa fully deployed position once with a jammed unlock actuator 24, afterwhich replacement of the unlock actuator is required. The landing gear10 is not permitted to again cycle from the fully deployed position to astowed position.

Although an example embodiment has been disclosed, a worker of ordinaryskill in this art would recognize that certain modifications would comewithin the scope of the claims. For that reason, the following claimsshould be studied to determine their true scope and content.

1. A landing gear system comprising: a landing gear strut rotatablebetween stowed and deployed positions; a lock-stay connected to thelanding gear strut and movable between locked and unlocked conditions;an actuator connected to the lock-stay including first and secondmembers movable relative to one another, the first member movablebetween first and second positions that correspond to the locked andunlocked conditions; and a controller in communication with the actuatorand configured to command the actuator between the first and secondpositions in response to an input, wherein the second member ispermitted to free-drive relative to the first member between the stowedand deployed positions with the lock-stay in the unlocked condition. 2.The landing gear system according to claim 1, comprising a two-wayactuator connected to the landing gear strut and configured to move thelanding gear strut between the stowed and deployed positions the secondmember configured to free-drive in response to movement of the two-wayactuator.
 3. The landing gear system according to claim 1, comprising alinkage connected to the landing gear strut, the lock-stayinterconnected between the linkage and the landing gear strut.
 4. Thelanding gear system according to claim 3, comprising a biasing membercooperating with the lock-stay to bias the lock-stay to the lockedcondition, the actuator overcoming a force exerted on the lock-stay bythe biasing member when moving from the first position to the secondposition.
 5. The landing gear system according to claim 1, wherein theactuator includes an electric motor coupled to the first member andconfigured to move the first member axially between the first and secondpositions, the second member moving axially in unison with the firstmember at least some distance between the first and second positions. 6.The landing gear system according to claim 5, wherein the first memberpulls the second member from the first position to the second positionduring a normal operating condition.
 7. The landing gear systemaccording to claim 5, wherein the first and second members are coaxialwith one another and nested relative to one another during the normaloperating condition, the second member decoupling from the first memberto free-drive relative to the first member when the first member is inan undesired position.
 8. The landing gear system according to claim 1,wherein the actuator comprises: a motor; a screw coupled to the motor; amember having a nut that is coupled to the screw, the member movablebetween first and second positions that correspond to locked andunlocked conditions; and a rod movable relative to the member during ajammed condition in which member is arranged in an undesired positionbetween the first and second positions, the rod being permitted tofree-drive relative to the member with the member in the undesiredposition.
 9. The landing gear system according to claim 8, wherein themember includes fingers and the rod is connected to a guide, the fingerand guide interlocking with one another under normal operatingconditions, and the fingers and guide decoupling from one another duringthe jammed condition permitting the rod to free-drive relative to themember.
 10. The landing gear system according to claim 9, wherein thejammed condition corresponds to the member in the undesired condition.11. The landing gear system according to claim 9, comprising a collardeflecting the fingers radially to engage the guide with hooks providedby the fingers.
 12. The landing gear system according to claim 9,wherein the member pulls the rod from the lock condition to the unlockcondition with the fingers and guide interlocked.
 13. The landing gearsystem according to claim 11, wherein the fingers include an undeflectedposition in the undesired position in which the member is spaced fromthe collar.
 14. The landing gear system according to claim 13, whereinthe guide is configured to slide past the hooks in the undesiredposition and free-drive relative to the member.
 15. The landing gearsystem according to claim 13, wherein the member and rod are coaxial andare nested relative to one another during normal operating conditions,the guide being blocked from being received in the member when the guideis arranged in a space between the collar and the member.
 16. Thelanding gear system according to claim 15, wherein the member occupiesthe space when in the second position during normal operation preventingthe guide from moving axially past the fingers.
 17. The landing gearsystem according to claim 8, comprising position sensors configured todetect a position of the member.